In matter over thread, how to use radio spinel driver?

[john.wong]

Host: ESP32S3
RCP: EFR32MG24 module
ESP-IDF: v5.5.4
ESP-Matter: release/v1.5

Hi,

Please check my steup above.
I am using esp32s3 as host and a silabs module as RCP. I have setup matter overthread and the device is running without issue.
I want to send/receive spinel commands to RCP in host application, for example, informing RCP to reset (SPINEL_CMD_RESET) or getting its firmware version (SPINEL_PROP_NCP_VERSION).
But I don't know which header should be included or what API I should be using.
Could you provide an example on above without affecting the original spinel communication?

Second, how to add custom vendor spinel command?
Thank you.